Polyester film as support for dry film resist

ABSTRACT

A polyester film for dry film resists, which satisfies requirements for transparency, particularly transmittance of radiation having a wavelength around 365 nm, slipperiness, winding properties, resolution and recyclability. A polyester film for dry film resists which has a thickness of 10 to 25 μm, a haze value of 3% or less and a residual polycondensation metal catalyst content of less than 150 ppm, and a metal antimony content of 15 mmol % or less based on the total of all the acid components, and a laminated polyester film comprising a lubricating layer on at least one side of the above film.

FIELD OF THE INVENTION

[0001] The present invention relates to a polyester film for dry filmresists. More specifically, it relates to a polyester film for dry filmresists, which is excellent in terms of transparency, slipperiness,winding properties, separation work efficiency and resolution.

PRIOR ART

[0002] In recent years, a dry film resist (may be abbreviated as DFRhereinafter) method has been used to produce a printed wiring circuitboard. A photoresist laminate used in this DFR method is generally alaminate structure comprising a base layer, a photoresist layer and aprotective layer laminated in the mentioned order and a polyester filmhaving excellent mechanical, chemical and optical properties has beenused as the base layer.

[0003] The DFR method comprises removing the protective layer of thephotoresist laminate having the above structure, oining the exposedphotoresist layer to a conductive matrix mounted on a substrate andjoining a glass sheet printed with an electronic circuit to thephotoresist film base layer. Thereafter, the resulting laminate wasexposed to ultraviolet radiation having a wavelength around 365 nm fromthe glass sheet side to exposure and cure a photosensitive resinconstituting the photoresist layer, the glass sheet and the base layerare removed, and an uncured portion of the photoresist layer is removedby a solvent or the like. Further, when etching is carried out with anacid, the exposed conductive matrix dissolves, the photoresist resinreacts, and an unremoved portion of the conductive matrix remains as itis. When the remaining photoresist layer is then removed by suitablemeans, the conductive matrix layer is formed on the substrate as acircuit.

[0004] A polyester film used as the base layer in the above DFR methodis required to have high transmission of light having a wavelengtharound 365 nm and a low haze value. When the photoresist layer is to beexposed, as light passes through the base layer, if the transmission ofthe base layer is low, the photoresist layer may not be exposed fully orlight may be scattered with the result of poor resolution.

[0005] In recent years, portable telephones, PHS and personal computershave been in growing demand and the improvement of productivity ofphotoresist films for the production of electronic circuits for use inthese devices has been required.

[0006] To improve handling ease for the production of photoresist filmsor the handling ease of a photoresist film, the polyester film of thebase layer is required to have moderate slipperiness, winding propertiesand tear strength. The method of forming fine protrusions on the surfaceof a polyester film by containing fine particles in the film has beenused to achieve the above properties. JP-A 7-333853 (the term “JP-A” asused herein means an “unexamined published Japanese patent application”)proposes a biaxially oriented laminated polyester film for photoresistsin which the outermost layer on at least one side contains particles(globular or amorphous silica particles, globular crosslinked polymerparticles, etc.) having an average particle diameter of 0.01 to 3.0 μmand has a surface roughness Ra (center line average roughness) of 0.005μm or more, an Rt (maximum height) of less than 1.5 μm and a film hazeof 1.5% or less.

[0007] However, this polyester film may be unsatisfactory in terms oftransmission of light having a wavelength around 365 nm with the resultof reduced resolution, thereby making it difficult to obtain a finecircuit pattern. Further, the above laminated polyester film has aproblem such as high production cost.

[0008] As the recent enactment of a home electric appliance recyclinglaw promotes the recycling of electric products and products forproducing the same, materials constituting these are required to containno antimony, tin or lead. Antimony compounds have been used as apolycondensation catalyst for producing a polyester polymer for forminga polyester film. Use of polycondensation catalysts other than theseantimony compounds is now desired.

SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide a polyesterfilm for dry film resists, which solves the above problems of the priorart and meets requirements for the transmission of light, especiallylight having a wavelength around 365 nm, slipperiness, windingproperties and resolution.

[0010] It is another object of the present invention to provide apolyester film for dry film resists, which further has excellentrecyclability in addition to the above properties.

[0011] It is still another object of the present invention to provide alaminated polyester film for dry film resists, which prevents reflectionand has excellent fine pattern circuit formability in addition to theabove properties.

[0012] It is a further object of the present invention to provide a dryfilm resist comprising the above polyester film of the present inventionas a base film.

[0013] Other objects and advantages of the present invention will becomeapparent from the following description.

[0014] According to the present invention, firstly, the above objectsand advantages of the present invention are attained by a biaxiallyoriented polyester film for dry film resists, which comprises (1) anaromatic polyester containing metals derived from a polycondensationcatalyst in a total amount of less than 150 ppm and metal antimony outof the above metals in an amount of 15 mmol % or less based on the totalof all the acid components and which has (2) a haze value of 3% or less,(3) a transmission of ultraviolet radiation having a wavelength of 365nm of 86% or more and (4) a thickness of 10 to 25 μm.

[0015] According to the present invention, secondly, the above objectsand advantages of the present invention are attained by a laminatedpolyester film which comprises (1) the above biaxially orientedpolyester film of the present invention and a lubricating layer formedon at least one side of the polyester film and which has (2) a hazevalue of 3% or less and (3) a transmittance of ultraviolet radiationhaving a wavelength of 365 nm of 86% or more.

[0016] According to the present invention, thirdly, the above objectsand advantages of the present invention are attained by a dry filmresist comprising the biaxially oriented polyester film or laminatedpolyester film of the present invention, a photoresist layer and aprotective film layer laminated in the mentioned order.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention will be described in detail hereinbelow. Adescription is first given of the biaxially oriented polyester film ofthe present invention.

[0018] The aromatic polyester constituting the film of the presentinvention is preferably a polyethylene terephthalate homopolymer or acopolymer comprising ethylene terephthalate as the main recurring unit.The polyethylene terephthalate homopolymer is suitably used in a DFRfilm because it has high mechanical strength and a high transmission ofshort-wavelength visible radiation and near ultraviolet radiation closeto that radiation.

[0019] In the present invention, the comonomer of the copolyester may bea dicarboxylic acid component or diol component. Examples of thedicarboxylic acid component include aromatic dicarboxylic acids such asisophthalic acid and phthalic acid; aliphatic dicarboxylic acids such asadipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid; andalicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.Examples of the diol component include aliphatic diols such as1,4-butanediol, 1,6-hexanediol and diethylene glycol; alicyclic diolssuch as 1,4-cyclohexanedimethanol; and aromatic diols such as bisphenolA. They may be used alone or in combination of two or more. Out ofthese, isophthalic acid is particularly preferred because it gives acopolymer having high transparency and tear strength.

[0020] The amount of the comonomer which depends on its type is suchthat the melting point of the obtained polymer should be 245 to 258° C.(melting point of the homopolymer). When the melting point is lower than245° C., heat resistance deteriorates, heat shrinkage becomes large andfilm flatness lowers.

[0021] The melting point of the polyester is measured by obtaining amelting peak at a temperature elevation rate of 20° C./min using the 910DSC of Du Pont Instruments Co., Ltd. The amount of the sample is about20 mg.

[0022] The intrinsic viscosity (orthochlorophenol, 35° C.) of thepolyester is preferably 0.52 to 1.50, more preferably 0.57 to 1.00,particularly preferably 0.60 to 0.80. When the intrinsic viscosity islower than 0.52, the tear strength may be insufficientdisadvantageously. When the intrinsic viscosity is higher than 1.50,productivity in the raw material production step and the film formationstep may be impaired.

[0023] The aromatic polyester such as polyethylene terephthalate orcopolyester in the present invention is not limited by its productionprocess. For instance, in the case of terephthalic acid, ethylene glycoland copolyester, a comonomer is further added to carry out anesterification reaction and then the obtained reaction product ispolycondensed until a targeted polymerization degree is achieved toproduce polyethylene terephthalate or copolyethylene terephthalate; orin the case of dimethyl terephthalate, ethylene glycol and copolyester,a comonomer is added to carry out an ester exchange reaction and thenthe obtained reaction product is polycondensed until a targetedpolymerization degree is achieved to produce polyethylene terephthalateor copolyethylene terephthalate. Polyethylene terephthalate orcopolyethylene terephthalate obtained by the above method (meltpolymerization) may be further polymerized in a solid state (solid-phasepolymerization) as required to produce a polymer having a higher degreeof polymerization.

[0024] The catalyst used for the above polycondensation reaction ispreferably a combination of a titanium compound (Ti compound), germaniumcompound (Ge compound), manganese compound (Mn compound) and antimonycompound (Sb compound), or a magnesium compound (Mg compound). Thesecatalysts may be used alone or in combination. Out of these, a germaniumcompound and a titanium compound are preferred and a germanium compoundis particularly preferred.

[0025] Preferred examples of the titanium compound include titaniumtetrabutoxide and titanium acetate. Preferred examples of the germaniumcompound include (a) amorphous germanium oxide, (b) fine crystallinegermanium oxide, (c) a solution of germanium oxide dissolved in glycolin the presence of an alkali metal, alkali earth metal or compoundthereof and (d) an aqueous solution of germanium oxide. Further, when 10mmol % or less of an antimony compound and/or a titanium compound are/isused, resolution can be improved and production cost can be reducedadvantageously.

[0026] The total content of the residual polycondensation metalcatalysts in the aromatic polyester is less than 150 ppm, preferably 30to 120 ppm, more preferably 50 to 100 ppm based on weight. Out of these,the content of metal antimony is 15 mmol % or less, preferably 10 mmol %or less, more preferably 5 mmol % or less, particularly preferably 0mmol % based on 1 mol of the total of all the acid components.

[0027] When the total content of the residual polycondensation metalcatalysts in the aromatic polyester is higher than 150 ppm, thetransmittance of radiation having a wavelength around 365 nm may becomeless than 86% based on a film thickness of 16 μm disadvantageously. Toreduce the total content of the residual polycondensation metalcatalysts in the aromatic polyester to 150 ppm or less, use of anantimony-based catalyst must be avoided, which is preferred from theviewpoint of the home electric appliance recycling law.

[0028] The above aromatic polyester may be optionally mixed withadditives such as an antioxidant, thermal stabilizer, viscositymodifier, plasticizer, color improving agent, lubricant and nucleatingagent.

[0029] Out of these, lubricant fine particles are added as the lubricantto secure the work efficiency (slipperiness) of the film. Any lubricantfine particles may be used. Inorganic lubricants include silica,alumina, titanium dioxide, calcium carbonate and barium sulfate. Organiclubricants include silicone resin particles and crosslinked polystyreneparticles. Out of these, porous silica particles which are agglomeratesof primary particles are particularly preferred. The porous silicaparticles have a characteristic property to improve the transparency ofthe film because voids are hardly produced around the particles when thefilm is stretched.

[0030] The average particle diameter of the primary particlesconstituting the porous silica particles is preferably in the range of0.001 to 0.1 μm. When the average particle diameter of the primaryparticles is smaller than 0.001 μm, extremely fine particles produced bythe cracking of a slurry agglomerate, causing a reduction intransparency. When the A, average particle diameter of the primaryparticles is larger than 0.1 μm, the porosity of the particles is lostwith the result that the feature that voids are hardly produced may belost. Further, the pore volume of the agglomerated particle ispreferably 0.5 to 2.0 ml/g, more preferably 0.6 to 1.8 ml/g. When thepore volume is smaller than 0.5 ml/g, the porosity of the particles islost, voids may be produced and transparency may be lowereddisadvantageously. When the pore volume is larger than 2.0 ml/g,cracking and agglomeration easily occur, thereby making it difficult tocontrol the diameter of the particle. The average particle diameter ofthe above porous silica particles is preferably in the range of 0.05 μmor more and less than 3.0 μm, more preferably 0.1 μm to 2.5 μm. Theamount of the porous silica particles is preferably 50 ppm or more andless than 1,000 ppm, more preferably 100 ppm to 800 ppm. When theaverage particle diameter is smaller than 0.05 μm, the amount of theporous silica particles must be increased to obtain high workefficiency, that is, slipperiness of the film, thereby impairingtransparency. When the average particle diameter is 3.0 μm or more,resolution may lower and the edge side of a conductor forming a circuitmay not be straight but jagged. When the amount of the porous silicaparticles is smaller than 50 ppm, the effect of providing slipperinessis hardly developed and when the amount is 1,000ppm or more,transparency may be impaired.

[0031] The porous silica may form coarse agglomerated particles such asa particle having an average particle diameter of 10 μm or more. Whenthe number of the coarse agglomerated particles is large, they cause areduction in resolution and a broken film. To reduce the number ofcoarse agglomerated particles, a nonwoven filter made of a stainlesssteel thin wire having a diameter of 15 μm or less and an averageopening size of 10 to 30 μm, preferably 13 to 28 μm, more preferably 15to 25 μm is used as a filter at the time of film formation to filter amolten polymer.

[0032] Preferably, the porous silica particles or other lubricantparticles are added to a reaction system (preferably as a glycol slurry)during a reaction for the production of a polyester, for example, at anytime during an ester exchange reaction or polycondensation reaction inthe case of the ester exchange method or at any time in the case of thedirect polymerization method. Particularly preferably, the porous silicaparticles are added to the reaction system in the initial stage of thepolycondensation reaction, for example, before the intrinsic viscosityof the polymer reaches about 0.3.

[0033] The thickness of the film of the preset invention is preferably10 μm to 25 μm. It is more preferably 13 μm to 23 μm, more preferably 14μm to 20 μm. When the thickness is larger than 25 μm, resolution lowersdisadvantageously. When the thickness is smaller than 10 μm, strengthbecomes insufficient and the film is frequently broken at the time ofstripping.

[0034] The haze value of the film of the present invention is 3% orless, preferably 1.5% or less, more preferably 1.0% or less.

[0035] The film of the present invention must have a transmission ofultraviolet radiation having a wavelength of 365 nm of 86% or more. Whenthe transmission is less than 86%, the exposure and curing step of aresist layer may not complete smoothly. The UV transmission of a filmhaving a thickness other than 16 μm is evaluated based on theLambert-Beer's law to calculate a value based on a thickness of 16 μmfrom the following equation:

log(Io/I)=εCd

[0036] wherein Io is the intensity of input light, I is the intensity oftransmitted light, ε is an absorptivity coefficient, C is aconcentration and d is the thickness of the film (μm).

[0037] Preferably, the film of the present invention has a degassingrate between films of 10 to 120 mmHg/hr. When the degassing rate iswithin the above range, the film is wound smoothly.

[0038] The degassing rate between films is obtained by piling up twenty8 cm×5 cm film pieces cut out from the film, making a regular triangularhole having a side length of 2 mm in the centers of 19 pieces exceptinga top piece from the above twenty film pieces and measuring a reductionin mmHg per unit time using a DIG-Thickness Tester (of Toyo Seiki Co.,Ltd.).

[0039] The above degassing rate can be easily achieved by adding theabove-described amount of inert fine particles having theabove-described particle diameter to the polyester.

[0040] Preferably, the film of the present invention has a thermalshrinkage factor in a longitudinal direction measured at 150° C. of 1.0to 5.0%. When the thermal shrinkage factor in the longitudinal directionis smaller than 1.0%, the flatness of the film may deteriorate and thetransparency of the film may degrade, thereby causing a trouble in theproduction process of a photoresist film and the production process ofan electronic circuit. When the thermal shrinkage factor in thelongitudinal direction is larger than 5.0%, the film is readily shrunkand deformed by heat and a solvent in each step.

[0041] The film of the present invention can be produced byconventionally known methods. For example, polyethylene terephthalate orcopolyethylene terephthalate containing lubricant fine particles isdried, molten, extruded and solidified by quenching on a cooling drum toobtain an unstretched film, biaxially orienting the unstretched film andheat setting the film.

[0042] More specifically, this unstretched film is stretched to 3 to 5times in a longitudinal direction at 70 to 130° C. and then to 3 to 5times in a transverse direction at 80 to 130° C. and heat set at190to240° C. to obtain a biaxially oriented film. Optionally, awater-dispersible coating is applied to one side or both sides of thefilm during the above step, for example, after stretching in thelongitudinal direction, to form a slippery, or slippery and adhesivecoating film as thick as 0.01 to 0.1 μm on the film. Coating is notlimited but coating with a reverse roll coater is preferred.

[0043] A description is subsequently given of the laminated polyesterfilm of the present invention. The laminated polyester film of thepresent invention has a lubricating layer formed on at least one side ofthe above biaxially oriented polyester film of the present invention asdescribed above.

[0044] The lubricating layer may comprise (A) a copolyester having aglass transition temperature of 40 to 80° C. and containing adicarboxylic acid component having a group represented by —SO₃M (M isthe same equivalent as —SO₃— of a metal atom, ammonium group, quaternaryorganic ammonium group or quaternary organic phosphonium group) in anamount of 8 to 20 mol % based on total of all the dicarboxylic acidcomponents, (B) an acrylic resin having a glass transition temperatureof 25 to 70° C., and (C) an inert particle lubricant.

[0045] More specifically, the lubricating layer may be formed byapplying a 4% aqueous solution (coating solution) which comprises 56parts by weight of a copolymer P of terephthalic acid, isophthalic acid,5-Na sulfoisophthalic acid (13 mol % based on the total of all thedicarboxylic acid components), ethylene glycol and neopentylene glycol(Tg=490° C.), 25 parts by weight of a copolymer S of methylmethacrylate, ethyl acrylate, acrylic acid, methacrylamide andN-methylolacrylamide (Tg=42° C.), 10 parts by weight of a crosslinkedacrylic resin filter (diameter of 40 nm) and 9 parts by weight of acopolymer of ethylene oxide and propylene oxide to one side of the abovefilm with a roll coater. The thickness of the layer film is preferably 5to 200 nm, the most preferably around 90 nm. This film thickness isequivalent to ¼ of the wavelength of ultraviolet radiation for making aresist layer insoluble when exposed thereto and makes reflected lightminimum. When the film thickness is smaller than 5 nm, slipperiness andthe effect of preventing reflection are hardly obtained. When thethickness is larger than 200 nm, light transmission lowers due tomulti-interference.

[0046] In the present invention, the lubricating layer can be formed onone side or both sides of the biaxially oriented polyester film of thepresent invention. When the lubricating layer is formed on both sides,the transmittance of radiation having a wavelength of 365 nm can beincreased. However, when the lubricating layer is formed on both sides,the peel strength of the photoresist layer may become high.

[0047] Preferably, the inert particle lubricant has an average particlediameter which is smaller than twice the thickness of the lubricatinglayer. Examples of the inert particles are the same as those listedabove.

[0048] The laminated polyester film of the present invention has anantimony metal content of preferably 15 mmol % or less, more preferably10 mmol % or less based on the total of all the acid components.

[0049] The laminated polyester film of the present invention must have atransmission of ultraviolet radiation having a wavelength of 365 nm of86% or more. When the UV transmission is less than 86%, the exposure andcuring step of the resist layer may not complete smoothly.

[0050] The laminated polyester film of the present invention has athermal shrinkage factor in a longitudinal direction measured afterheating at 150° C. for 30 minutes of preferably 2% or less, morepreferably 1.5% or less. When the thermal shrinkage in the longitudinaldirection is higher than 2%, wavy wrinkles with mountains and valleysparallel to one another in a longitudinal direction may be formed whilethe film is processed for DFR application, whereby the flatness of thefilm may be impaired.

[0051] Preferably, the number of flyspecks having a long diameter of 20μm or more contained in the laminated polyester film of the presentinvention is preferably 10 or less per 10 cm². The number of flyspeckshaving a long diameter of 20 μm or more is preferably as small aspossible because they prevent light from going straight and cause acircuit defect. Since the flyspecks are generated from foreign matter.undissolved polymer or coarse particles as a nucleus, it is preferred toremove coarse particles and foreign matter by using the above-describednonwoven filter.

[0052] It should be understood that the above description of thebiaxially oriented polyester film is applied to what is not described ofthe laminated polyester film directly or with modifications obvious topeople of ordinary skill in the art.

[0053] Both of the above biaxially oriented polyester film and thelaminated polyester film of the present invention are advantageouslyused as a base layer for the production of a dry film resist asdescribed above.

[0054] Therefore, according to the present invention, there are provideda dry film resist comprising the biaxially oriented polyester film ofthe present invention, a photoresist layer and a protective film layer,and a dry film resist comprising the laminated polyester film of thepresent invention, a photoresist layer and a protective film layerlaminated in the mentioned order, wherein when the laminated polyesterfilm has a lubricating layer on only one side, the photoresist layer isexistent on a side devoid of the lubricating layer.

[0055] The photoresist layers of the above dry film resists may beformed by applying a photoresist to a base layer in accordance with amethod known per se. The protective film is provided to protect the thusformed photoresist layer until the dry film is used.

[0056] The photoresist layer in the present invention may be made from aknown photosensitive resin composition but preferably it comprises (A) abinder polymer, (B) a photopolymerization initiator and (C) aphotopolymerization compound having at least one polymerizableethylenically unsaturated group in the molecule as essentialingredients, so that the layer can be developed by dilute alkalisolution.

[0057] Examples of the above binder polymer (A) include an acrylicresin, styrene-based resin, epoxy-based resin, amide-based resin,amide-epoxy-based resin, alkyd-based resin and phenolic resin. Anacrylic resin is preferred from the viewpoint of alkali developability.They may be used alone or in combination of two or more.

[0058] The above binder polymer may be produced by radical polymerizinga polymerizable monomer. Examples of the above polymerizable monomerinclude styrene, polymerizable styrene derivatives having a substituentat the α-position or in the aromatic ring, such as α-methylstyrene andvinyltoluene, acrylamides such as diacetone acrylamide, acrylonitrile,vinyl alcohol ethers such as vinyl-n-butyl ether, (meth)acrylic acidalkyl esters, (meth)acrylic acid tetrahydrofurfuryl esters,(meth)acrylic acid dimethyl aminoethyl esters, (meth)acrylic aciddiethyl aminoethyl esters, (meth)acrylic acid glycidyl esters,2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl(meth)acrylate, (meth)acrylic acid, α-bromo(meth)acrylic acid,α-chloro(meth)acrylic acid, β-furyl(meth)acrylic acid,β-styryl(meth)acrylic acid, maleic acid, maleic acid anhydride, maleicacid monoesters such as monomethyl maleate, monoethyl maleate andmonoisopropyl maleate, fumaric acid, cinnamic acid, α-cyanocinnamicacid, itaconic acid, crotonic acid and propiolic acid.

[0059] Among the above (meth)acrylic acid alkyl esters are compoundsrepresented by the following formula (I) and compounds obtained bysubstituting the alkyl groups of the compounds with a hydroxyl group,epoxy group or halogen group:

[0060] wherein R¹ is a hydrogen atom or methyl group, and R² is an alkylgroup having 1 to 12 carbon atoms. Examples of the alkyl group having 1to 12 carbon atoms represented by R² in the above formula (I) includemethyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl,decyl, undecyl, dodecyl and structural isomers thereof.

[0061] The monomers represented by the above formula (I) include(meth)acrylic acid methyl esters, (meth)acrylic acid ethyl esters,(meth)acrylic acid propyl esters, (meth)acrylic acid butylesters,(meth)acrylic acid pentyl esters, (meth)acrylic acid hexyl esters,(meth)acrylic acid heptyl esters, (meth)acrylic acid octyl esters,(meth)acrylic acid 2-ethylhexyl esters, (meth)acrylic acid nonyl esters,(meth)acrylic acid decyl esters, (meth)acrylic acid undecyl esters and(meth)acrylic acid dodecyl esters. They may be used alone or incombination of two or more.

[0062] The above binder polymer (A) preferably contains a carboxyl groupfrom the viewpoint of alkali developability and may be produced, forexample, by radical polymerizing a polymerizable monomer having acarboxyl group and another polymerizable monomer. The binder polymer (A)preferably contains styrene or a styrene derivative as the polymerizablemonomer from the viewpoint of flexibility.

[0063] The above binder polymers (A) may be used alone or in combinationof two or more.

[0064] Examples of the above photopolymerization initiator (B) includearomatic ketones (such as benzophenone,4,4′-bisdimethylaminobenzophenone (Michler's ketone),4,4′-bisdiethylaminobenzophenone,4-methoxy-4′-dimethylaminobenzophenone, 2-ethylanthraquinone andphenanthrenequinone), benzoin ethers (such as benzoin methyl ether,benzoin ethyl ether and benzoin phenyl ether), benzoins (such as methylbenzoin and ethyl benzoin), benzyl derivatives (such as benzyl dimethylketal), 2,4,5-triarylimidazole dimers (such as2-(o-chlorophenyl)-4,5-diphenylimidazole dimer,2-(o-chlorophenyl)-4,5-di(m-methoxyphenyl)imidazole dimer,2-(o-fluorophenyl)-4,5-diphenylimidazole dimer,2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer,2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer,2,4-di(p-methoxyphenyl)-5-phenylimidazole dimer,2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer and2-(p-methylmercaptophenyl)-4,5-diphenylimidazole dimer), and acridinederivatives (such as 9-phenylacridine and1,7-bis(9,9′-acridinyl)heptane). They may be used alone or incombination of two or more.

[0065] Examples of the above photopolymerization compound having atleast one polymerizable ethylenically unsaturated group in the molecule(C) include compounds obtained by reacting a polyhydric alcohol with anα,β-unsaturated carboxylic acid, compounds obtained by reacting a2,2-bis(4-((meth)acryloxypolyethoxy)phenyl)propane and a glycidylgroup-containing compound with an α,β-unsaturated carboxylic acid,urethane monomers, nonylphenyl dioxylene (meth)acrylate,γ-chloro-β-hydroxypropyl-β′-(meth)acryloyloxyethyl-o-phthalate,β-hydroxyethyl-β′- (meth)acryloyloxyethyl-o-phthalate,β-hydroxypropyl-β′-(meth)acryloyloxyethyl-o-phthalate and (meth)acrylicacid alkyl esters.

[0066] The above compounds obtained by reacting a polyhydric alcoholwith an α,β-unsaturated carboxylic acid include polyethylene glycoldi(meth)acrylates having 2 to 14 ethylene groups, polypropylene glycoldi(meth)acrylates having 2 to 14 propylene groups, trimethylolpropanedi(meth)acrylate, trimethylolpropane tri(meth)acrylate,trimethylolpropane ethoxy tri(meth)acrylate, trimethylolpropane diethoxytri(meth)acrylate, trimethylolpropane triethoxy tri(meth)acrylate,trimethylolpropane tetraethoxy tri(meth)acrylate, trimethylolpropanepentaethoxy tri(meth) acrylate, tetramethylolmethane tri(meth) acrylate,tetramethylolmethane tetra(meth)acrylate, polypropylene glycoldi(meth)acrylates having 2 to 14 propylene groups, dipentaerythritolpenta(meth) acrylate and dipentaerythritol hexa(meth)acrylate.

[0067] Examples of the above α,β-unsaturated carboxylic acid include(meth)acrylic acid. Examples of the above2,2-bis(4-((meth)acryloxypolyethoxy)phenyl) propane include2,2-bis(4-((meth)acryloxydiethoxy)phenyl)propane,2,2-bis(4-((meth)acryloxytriethoxy)phenyl)propane,2,2-bis(4-((meth)acryloxypentaethoxy)phenyl)propane and2,2-bis(4-((meth)acryloxydecaethoxy)phenyl.2,2-bis(4-(methacryloxypentaethoxy)phenyl)propane is commerciallyavailable under the name of BPE-500 (trade name of Shin Nakamura KagakuKogyo Co., Ltd.).

[0068] Examples of the above glycidyl group-containing compound includetrimethylolpropane triglycidyl ether tri(meth)acrylate and2,2-bis(4-(meth)acryloxy-2-hydroxy-propyloxy)phenyl. The above urethanemonomers include addition reaction products of a (meth)acryl monomerhaving an OH group at the β-position and isophorone diisocyanate,2,6-toluene diisocyanate, 2,4-toluene diisocyanate or 1,6-hexamethylenediisocyanate, tris((meth)acryloxy tetraethylene glycolisocyanate)hexamethylene isocyanurate, EO modified urethanedi(meth)acrylates and EO and PO modified urethane di(meth)acrylates. EOstands for ethylene oxide and the EO modified compounds have the blockstructure of an ethylene oxide group. PO stands for propylene oxide andthe PO modified compounds have the block structure of a propylene oxidegroup.

[0069] The above (meth)acrylic acid alkyl esters include (meth)acrylicacid methyl esters, (meth)acrylic acid ethyl esters, (meth)acrylic acidbutyl esters and (meth)acrylic acid 2-ethylhexyl esters. They may beused alone or in combination of two or more.

[0070] In the present invention, the amount of the component (A) ispreferably 40 to 80 parts by weight based on 100 parts by weight of thetotal of the components (A) and (C). When the amount is smaller than 40parts by weight, an optically cured product readily becomes brittle andif it is used as a photosensitive element, coatability may deteriorate.When the amount is larger than 80 parts by weight, sensitivity maybecome insufficient.

[0071] The amount of the component (B) is preferably 0.1 to 20 parts byweight based on 100 parts by weight of the total of the components (A)and (C). When the amount is smaller than 0.1 part by weight, sensitivitymay become insufficient and when the amount is larger than 20 parts byweight, absorption by the surface of the composition upon exposureincreases, whereby the optical curing of the interior may becomeunsatisfactory.

[0072] The amount of the component (C) is preferably 20 to 60 parts byweight based on 100 parts by weigh of the total of the components (A)and (C). When the amount is smaller than 20 parts by weight, sensitivitymay become insufficient and when the amount is larger than 60 parts byweight, an optically cured product may become brittle.

[0073] The photosensitive resin composition in the present invention mayoptionally contain a dye such as Malachite Green, optically colordeveloping agent such as tribromophenyl sulfone or leucocrystal violet,thermal color development preventing agent, plasticizer such asp-toluene sulfonamide, pigment, filler, antifoamer, flame retardant,stabilizer, adhesion providing agent, leveling agent, release promotingagent, antioxidant, perfume, imaging agent and thermal crosslinkingagent in an amount of 0.01 to 20 parts by weight each based on 100 partsby weight of the total of the components (A) and (C). They may be usedalone or in combination of two or more.

[0074] The photosensitive resin composition of the present invention maybe dissolved in a solvent such as methanol, ethanol, acetone, methylethyl ketone, methyl cellosolve, ethyl cellosolve, toluene, N-dimethylformamide or propylene glycol monomethyl ether, or a mixed solventthereof and applied as a solution having a solid content of 30 to 60 wt%.

[0075] The thickness of the photoresist layer which differs according toapplication purpose is preferably 1 to 100 μm, more preferably 3 to 100μm, particularly preferably 5 to 100 μm after it is dried.

[0076] The flowability of the photoresist layer is preferably 50 to 500μm, more preferably 100 to 300 μm, particularly preferably 100 to 250 μmfrom the viewpoints of followability to an adherent such as a substrate,low deformability of the photoresist layer and low edge fusibility. Theflowability can be controlled to the above range by adjusting the typeand amount of each component constituting the photoresist layer. Theflowability is defined as T₁-T₂ (μm) when a photoresist layer having adiameter of 20 mm and a thickness of 2 mm is used as a sample, thissample is placed on a flat substrate, a 5 kg cylindrical static loadhaving a diameter of 50 mm is applied to the sample, and the thickness(T₁ μm) of the deforming photoresist layer after 10 seconds and thethickness (T₂ μm) of the photoresist layer after 900 seconds aremeasured.

EXAMPLES

[0077] The following examples are given to further illustrate thepresent invention. Various physical property values and characteristicproperties in the present invention were measured and defined asfollows.

[0078] (1) Determination Analysis of Antimony

[0079] The film is melt molded to manufacture a plate having a diameterof 5 cm and a thickness of 3 mm and the amount of antimony is determinedby measuring it with fluorescent X-radiation (RIX3000 of Rigaku DenkiCo., Ltd.). The used X-ray bulb is preferably a Cr or Rh bulb but otherX-ray bulbs may be used if they can determine the amount of antimony.Determination analysis is carried out by drawing a calibration curvefrom a sample whose amount of antimony is already known (axis ofabscissa: amount of antimony, axis of ordinates: detected amount ofantimony at the time of analysis (unit: cps)) and determining the amountof antimony from the detected amount (unit: cps) of antimony containedin an unknown sample.

[0080] (2) Average Particle Diameter of Particles

[0081] This is measured using the CP-50 centrifugal particle sizeanalyzer of Shimadzu Corporation. The particle diameter equivalent to 50mass percent is read from the accumulative curve of the particlediameter and amount of particles of each size calculated from theobtained centrifugal sedimentation curve and taken as the above averageparticle diameter (“Particle Size Measurement Technology” published byNikkan Kogyo Shimbun Co., Ltd., pp. 242-247, 1975).

[0082] When the inert fine particles as a lubricant added are secondaryparticles which are agglomerates of primary particles, the particlediameter obtained by the above average particle diameter measuringmethod may be smaller than the actual average particle diameter.Therefore, the following method is employed.

[0083] Agglomerates (secondary particles) of particles contained in asuper thin piece having a thickness in a sectional direction of 100 nmobtained from the film containing the particles are observed through atransmission electron microscope (for example, the JEM-1200EX of JEOLLtd.) at a magnification of about ×10,000. Using this microphotograph,the diameters equivalent to the area of a circle of 1,000 particles aremeasured with an image analyzer and the number average particle diameterof these particles is taken as average secondary particle diameter. Thetype of the particles may be identified by the quantitative analysis ofa metal element by SEM-XMA or ICP. The average primary particle diameteris measured in accordance with the method of measuring average secondaryparticle diameter except that the particles are imaged by a transmissionelectron microscope at a magnification of ×100,000 to ×1,000,000.

[0084] (3) Film Thickness

[0085] The thickness of the film is measured at 100 points by anexternal micrometer and the average of the measurement values isobtained as the thickness of the film.

[0086] (4) Degassing Rate of Film

[0087] The winding properties of the film is expressed by degassing timewhen the films overlap with one another. The degassing rate is obtainedby piling up twenty 8 cm×5 cm film pieces cut out from the film, makinga regular triangular hole having a side length of 2 mm in the centers of19 pieces excepting a top piece from the above twenty film pieces andmeasuring a reduction in mmHg per unit time using a DIG-Thickness Tester(of Toyo Seiki Co., Ltd.).

[0088] (5) UV Transmission

[0089] The transmission of ultraviolet radiation having a wavelength of365 nm is measured with the MPC-3100 spectrophotometer of ShimadzuCorporation.

[0090] (6) Haze Value

[0091] The haze value of the film is measured with the NDH-20 haze meterof Nippon Denshoko Kogyo Co., Ltd. This is measured in accordance withJIS P-8116.

[0092] (7) Thermal Shrinkage Factor

[0093] The film whose length has been measured accurately is placed in athermostatic chamber set to 1500° C. under no tension, kept there for 30minutes, taken out from the chamber and returned to normal temperatureto read its dimensional change. The thermal shrinkage factor of the filmis obtained from the following equation when the length before the heattreatment is represented by L₀ and the length after the heat treatmentis represented by L.

thermal shrinkage=(L ₀ −L) ×100/L ₀ (%)

[0094] (8) Melting Point

[0095] This is measured by obtaining a melting peak at a temperatureelevation rate of 20° C./min using the 910 DSC of Du Pont InstrumentsCo., Ltd. The amount of the sample is about 20 mg.

[0096] (9) Characteristic Properties of Photoresist Film

[0097] The obtained photoresist film is used to manufacture a printedcircuit so as to evaluate its resolution and circuit defect. That is,the photoresist layer of the photoresist film whose protective layer hasbeen removed is joined to a copper sheet formed on a glassfiber-containing epoxy resin plate, a glass sheet printed with a circuitis joined to the photoresist film, the obtained assembly is exposed toultraviolet radiation from the glass sheet side, the photoresist film isremoved, the resin plate is washed and etched to form a circuit, andresolution and a circuit defect are observed visually and through amicroscope to evaluate the characteristic properties of the photoresistfilm based on the following criteria.

[0098] (a) resolution

[0099] ⊚: resolution is extremely high and a clear circuit is obtained

[0100] ◯: resolution is high and a clear circuit is obtained

[0101] Δ: clearness is slightly low and a phenomenon such as a bold lineis seen

[0102] X: clearness is low and a practically usable circuit cannot beobtained

[0103] (b) circuit defect

[0104] ◯: no circuit defect is observed

[0105] Δ: some circuit defects are observed

[0106] X: a large number of circuit defects are observed and the circuitcannot be used

Example 1

[0107] Dimethyl terephthalate and ethylene glycol were polymerized inaccordance with a commonly used method by adding manganese acetate as anester exchange catalyst, germanium oxide as a polymerization catalyst,phosphorous acid as a stabilizer and 0.066 wt % based on the polymer ofporous particles having an average particle diameter of 1.7 μm aslubricant agglomerated particles to obtain polyethylene terephthalatehaving an intrinsic viscosity (orthochlorophenol, 350° C.) of 0.65. Apellet of this polyethylene terephthalate was dried at 170° C. for 3hours, supplied to an extruder, molten at a temperature of 295° C.,filtered with a nonwoven filter having an average opening size of 24 μmand made of a stainless steel thin wire having a diameter of 13 μm, andextruded from a T die onto a rotary cooling drum having a surface finishof about 0.3 s and a surface temperature of 20° C. to obtain a 225μm-thick unstretched film. The thus obtained unstretched film waspreheated at 75° C., stretched to 3.6 times between a low-speed rollerand a high-speed roller by heating with. a single infrared heater havinga surface temperature of 800° C. from 15 mm above, quenched and suppliedto a stenter to be stretched to 3.9 times in a transverse direction at120° C. The obtained biaxially oriented film was heat set at 205° C. for5 seconds to obtain a 16 μm-thick biaxially oriented polyester film. Aphotoresist layer and a protective layer were formed on one side of thisfilm to manufacture a printed circuit so as to evaluate itscharacteristic properties. The evaluation results of the printed circuitand the characteristic properties of the film alone are shown in Table1.

Example 2

[0108] A 19 μm-thick biaxially oriented polyester film made frompolyethylene terephthalate was obtained in the same manner as inExample 1. A photoresist layer and a protective layer were formed onthis film to manufacture a printed circuit so as to evaluate itscharacteristic properties. The evaluation results of the printed circuitand the characteristic properties of the film alone are shown in Table1.

Example 3

[0109] A 14 μm-thick biaxially oriented polyester film was obtained inthe same manner as in Example 1 except that antimony trioxide was addedto a catalyst of Example 1 in an amount shown in Table 1 and thefollowing coating solution was applied to one side of the film stretchedin a longitudinal direction as a lubricant coating to a thickness of0.05 μm after drying and stretching in a transverse direction. Aphotoresist layer and a protective layer were formed on one side of thisfilm to manufacture a printed circuit so as to evaluate itscharacteristic properties. The evaluation results of the printed circuitand the characteristic properties of the film alone are shown inTable 1. coating solution: a 4% aqueous solution comprising 56 parts byweight of a copolymer P of terephthalic acid, isophthalic acid, 5-Nasulfoisophthalic acid (13 mol % based on the total of all thedicarboxylic acid components), ethylene glycol and neopentylene glycol(Tg=49° C.), 25 parts by weight of a copolymer S of methyl methacrylate,ethyl acrylate, acrylic acid, methacrylamide and N-methylolacrylamide(Tg=42° C.), 10 parts by weight of a crosslinked acrylic resin filter(diameter of 40 nm) and 9 parts by weight of a copolymer of ethyleneoxide and propylene oxide.

Example 4

[0110] A 12 μm-thick biaxially oriented polyester film was obtained inthe same manner as in Example 1 except that polyethylene terephthalateobtained by copolymerizing 3 mol % of isophthalic acid was used and alubricant shown in Table 1 was added. A photoresist layer and aprotective layer were formed on this film to manufacture a printedcircuit so as to evaluate its characteristic properties. The evaluationresults of the printed circuit and the characteristic properties of thefilm alone are shown in Table 1.

[0111] Not shown in the table, the degassing rates of Examples 1 to 4were in the range of 30 to 100 mmHg/hr advantageously. ComparativeExample 1

[0112] An unstretched film was obtained in the same manner as in Example1 except that antimony trioxide was used as a condensation catalyst.This unstretched film was preheated at 75° C., stretched to 3.6 timesbetween a low-speed roller and a high-speed roller by heating with asingle infrared heater having a surface temperature of 800° C. from 15mm above, quenched and supplied to a stenter to be stretched to 3.9times in a transverse direction at 120° C. The obtained biaxiallyoriented film was heat set at 205° C. for 5 seconds to obtain a 16μm-thick biaxially oriented polyester film. A photoresist layer and aprotective layer were formed on one side of this film to manufacture aprinted circuit so as to evaluate its characteristic properties. Theevaluation results of the printed circuit and the characteristicproperties of the film alone are shown in Table 1. When this film wasused as a base film for a photoresist, it deteriorated the quality of aprinted board due to poor resolution. Comparative Examples 2 to 4

[0113] Polyethylene terephthalate films having thicknesses shown inTable 1 were obtained in the same manner as in Example 1 except thatlubricants shown in Table 1 were used. A photoresist layer and aprotective layer were formed on these films to manufacture printedcircuits so as to evaluate their characteristic properties. Theevaluation results of the printed circuits and the characteristicproperties of the films alone are shown in Table 1.

[0114] The same coating as in Example 3 was applied to one side of thefilm after stretching in a longitudinal direction in

Comparative Example 4

[0115] The film of Comparative Example 2 had a high haze value, lowresolution and a circuit defect.

[0116] The film of Comparative Example 3 was too thick and had lowresolution.

[0117] The film of Comparative Example 4 was too thin and brokefrequently when it was separated from a resist. Therefore, a printedcircuit could not be manufactured.

Comparative Example 5

[0118] An attempt was made to produce a film in the same manner as inExample 1 except that polyethylene terephthalate obtained bycopolymerizing 23 mol % of isophthalic acid was used and a catalystshown in Table 1 was used. However, break occurred frequently duringfilm formation and it was difficult to manufacture a printed circuit.TABLE 1 content of content lubricant characteristic melting residual ofSb average existence UV properties point of catalyst in film particle ofthick- haze trans- of photoresist film polyester polyester in film mmoldiameter amount slippery ness value mission circuit composition ° C. ppm% type (μm) ppm layer μm % % resolution defect Ex. 1 PET 258 100 0porous silica 1.7 660 nonexistent 16 2.3 88.1 ◯ ◯ Ex. 2 PET 258 100 0porous silica 1.7 660 nonexistent 19 2.6 87.1 ◯ ◯ Ex. 3 PET 258 140 10porous silica 1.7 330 existent 14 1.4 88.2 ◯ ◯ Ex. 4 PET/IA₃ 250 120 0porous silica 2.3 720 nonexistent 12 3.2 86.8 ◯ ◯ C. Ex. 1 PET 258 30020 porous silica 1.7 660 nonexistent 16 2.4 85.4 X ◯ C. Ex. 2 PET 258120 0 kaolin clay 0.6 2500 nonexistent 16 6.0 84.3 X X C. Ex. 3 PET 258100 0 porous silica 1.7 660 nonexistent 38 3.5 85.8 X Δ C. Ex. 4 PET 258100 0 porous silica 0.5 300 existent 8 0.9 88.4 — — C. Ex. 5 PET/IA₂₃198 200 15 porous silica 1.7 660 nonexistent 16 3.6 81.2 — —

Example 5

[0119] Dimethyl terephthalate and ethylene glycol were polymerized byadding manganese acetate as an ester exchange catalyst, germanium oxideas a polymerization catalyst, phosphorous acid as a stabilizer, 25 ppmbased on the polymer of porous silica particles having an averageparticle diameter of 1.7 μm and 80 ppm based on the polymer of globularsilica having an average particle diameter of 0.12 μm as lubricantagglomerated particles in accordance with a commonly used method toobtain polyethylene terephthalate having an intrinsic viscosity(orthochlorophenol, 35° C.) of 0.65. A pellet of this polyethyleneterephthalate was dried at 170° C. for 3 hours, supplied to an extruder,molten at a temperature of 295° C., filtered with a nonwoven filterhaving an average opening size of 24 μm and made of a stainless steelthin wire having a diameter of 13 μm, and extruded from a T die onto arotary cooling drum having a surface finish of about 0.3 s and a surfacetemperature of 20° C. to obtain a 225 μm-thick unstretched film. Thethus obtained unstretched film was preheated at 75° C. and stretched to3.6 times between a low-speed roller and a high-speed roller by heatingwith a single infrared heater having a surface temperature of 800° C.from 15 mm above, the following coating solution was applied to one sideof the film stretched in a longitudinal direction as a lubricant coatingto a thickness of 40 nm after drying and stretching in a transversedirection, and the coated film was then supplied to a stenter to bestretched to 3.9 times in a transverse direction at 120° C. The obtainedbiaxially oriented film was heat set at 230° C. for 5 seconds to obtaina 16 μm-thick biaxially oriented polyester film. A photo resist layerand a protective layer were formed on one side devoid of the lubricatingcoating film of this film to manufacture a printed circuit so as toevaluate its characteristic properties. The evaluation results of theprinted circuit and the characteristic properties of the film alone areshown in Table 2. coating solution: a 4% aqueous solution comprising 56parts by weight of a copolymer P of terephthalic acid, isophthalic acid,5-Na sulfoisophthalic acid (13 mol % based on the total of all thedicarboxylic acid components), ethylene glycol and neopentylene glycol(Tg=49° C.), 25 parts by weight of a copolymer S of methyl methacrylate,ethyl acrylate, acrylic acid, methacrylamide and N-methylolacrylamide(Tg=42° C.), 10 parts by weight of a crosslinked acrylic resin filter(diameter of 40 nm) and 9 parts by weight of a copolymer of ethyleneoxide and propylene oxide.

Example 6

[0120] A 23 μm-thick biaxially oriented polyester film made frompolyethylene terephthalate was obtained in the same manner as in Example5. A photoresist layer and a protective layer were formed on one sidedevoid of a lubricant of this film to manufacture a printed circuit soas to evaluate its characteristic properties. The evaluation results ofthe printed circuit and the characteristic properties of the film aloneare shown in Table 2.

Example 7

[0121] A 19 μm-thick biaxially oriented polyester film was obtained inthe same manner as in Example 5. A photoresist layer and a protectivelayer were formed on one side devoid of a lubricating layer of this filmto manufacture a printed circuit so as to evaluate its characteristicproperties. The evaluation results of the printed circuit and thecharacteristic properties of the film alone are shown in Table 2.

Example 8

[0122] A 12 μm-thick biaxially oriented polyester film was obtained inthe same manner as in Example 5 except that polyethylene terephthalatecontaining 3 mol % of isophthalic acid was used and a lubricant shown inTable 2 was added. A photoresist layer and a protective layer wereformed in this film to manufacture a printed circuit so as to evaluateits characteristic properties. The evaluation results of the printedcircuit and the characteristic properties of the film alone are shown inTable 2.

[0123] The degassing rates of the films of Examples 1 to 4 were in therange of 30 to 100 mmHg/hr advantageously. The thermal shrinkage factorsafter the films were heated at 150° C. for 30minutes were less than2% inboth longitudinal and transverse directions.

Comparative Example 6

[0124] A 225 μm-thick unstretched film was obtained in the same manneras in Example 5 except that only porous silica having an averageparticle diameter of 1.7 μm was used in an amount of 660 ppm. Thisunstretched film was preheated at 75° C. and stretched to 3.6 timesbetween a low-speed roller and a high-speed roller by heating with asingle infrared heater having a surface temperature of 800° C. from 15mm above, the above coating solution was applied to one side of the filmstretched in a longitudinal direction as a lubricant coating to athickness of 40 nm after drying and stretching in a transversedirection, and the coated film was supplied to a stenter to be stretchedto 3.9 times in a transverse direction at 120° C. The obtained biaxiallyoriented film was heat set at 205° C. for 5 seconds to obtain a 16μm-thick biaxially oriented polyester film. A photoresist layer and aprotective layer were formed on a side devoid of the lubricant of thisfilm to manufacture a printed circuit so as to evaluate itscharacteristic properties. The evaluation results of the printed circuitand the characteristic properties of the film are shown in Table 2. Whenthis film was used in DFR, it deteriorated the quality of a printedboard due to poor resolution.

Comparative Example 7

[0125] A 23 μm-thick polyethylene terephthalate film was obtained in thesame manner as in Example 5 except that antimony trioxide was used as acatalyst and a lubricating layer was not applied. A photoresist layerand a protective layer were formed on this film to manufacture a printedcircuit so as to evaluate its characteristic properties. The evaluationresults of the printed circuit and the characteristic properties of thefilm are shown in Table 2. The transmission of ultraviolet radiationhaving a wavelength of 365 nm could not reach a target value.

Comparative Example 8

[0126] Kaolin clay was used as a lubricant. The film had a too largehaze value and a circuit defect.

Comparative Example 9

[0127] A film was formed in the same manner as in Example 5 except thatits thickness was changed to 30 μm, and a photoresist layer and aprotective layer were formed on a side devoid of a lubricant of thisfilm to manufacture a printed circuit so as to evaluate itscharacteristic properties. The evaluation results of the printed circuitand the characteristic properties of the film are shown in Table 2. Thefilm had low resolution and a circuit defect.

Comparative Example 10

[0128] A 9 μm-thick polyester film having a lubricating layer on bothsides was obtained using the polymer and lubricant shown in Table 2. Thefilm broke when it was separated from a photoresist layer and could notbe evaluated. TABLE 2 lubricant content average lubricating layer UVcharacteristic properties of of Sb in particle thick- thick- haze trans-photoresist film polyester film diameter amount ness ness value missionreso- circuit composition mmol % type μm ppm side nm μm % % lutiondefect releasability Ex. 5 PET 0 porous silica 1.7 25 one side 40 16 0.388 ◯ ◯ ◯ globular silica 0.12 80 Ex. 6 PET 0 porous silica 1.7 20 oneside 40 23 0.5 88 ◯ ◯ ◯ globular silica 0.2 70 Ex. 7 PET 0 porous silica1.7 23 one side 40 19 0.4 87 ◯ ◯ ◯ globular silica 0.12 75 Ex. 8 PET/IA₃0 porous silica 2.3 30 one side 90 12 0.4 88 ◯ ◯ ◯ globular silica 0.180 C. Ex. 6 PET 0 porous silica 1.7 660 one side 40 16 1.8 85 Δ ◯ ◯ — C.Ex. 7 PET 20 porous silica 1.7 25 none — 23 0.3 82 X Δ ◯ globular silica0.12 80 C. Ex. 8 PET 0 kaolin clay 0.6 2500 one side 40 16 3.5 79 X X ◯— C. Ex. 9 PET 0 porous silica 1.7 25 one side 40 30 1.4 85 X Δ ◯globular silica 0.12 80 C. Ex. 10 PET/IA₁₂ 0 porous silica 4.1 25 bothsides 90 9 1.6 89 — — X globular silica 0.1 80

[0129] As described above, according to the present invention, thepolyester film of the present invention satisfies requirements for UVtransmission, winding properties and conveyance work efficiency at thesame time, makes it possible to produce a defect-free circuit with highresolution when it is used in a fine pattern photoresist, can obtainhigh production yield and accordingly has a high industrial value.

1. A biaxially oriented polyester film for dry film resists, whichcomprises (1) an aromatic polyester containing metals derived from apolycondensation catalyst in a total amount of less than 150 ppm basedon weight and antimony out of the above metals in an amount of 15 mmol %or less based on the total of all the acid components and which has (2)a haze value of 3% or less, (3) a transmittance of ultraviolet radiationhaving a wavelength of 365 nm of 86% or more and (4) a thickness of 10to 25 μm.
 2. The biaxially oriented polyester film of claim 1 in whichthe metal(s) derived from a polycondensation catalyst is (are) at leastone metal selected from the group consisting of titanium, germanium,manganese, antimony and magnesium.
 3. The biaxially oriented polyesterfilm of claim 1, wherein the metal(s) derived from a polycondensationcatalyst is (are) contained in an amount of 30 to 120 ppm based onweight.
 4. The biaxially oriented polyester film of claim 1 whichcontains metal antimony in an amount of about 0 mmol % based on thetotal of all the acid components.
 5. The biaxially oriented polyesterfilm of claim 1 which has a haze value of 1.5% or less.
 6. The biaxiallyoriented polyester film of claim 1 which has a transmittance ofultraviolet radiation having a wavelength of 365 nm of 86 to 93%.
 7. Thebiaxially oriented polyester film of claim 1 which has a thickness of 13to 23 μm.
 8. The biaxially oriented polyester film of claim 1 whichfurther contains inert particles having an average particle diameter of0.05 to 3.0 μm in an amount of 50 ppm or more and less than 1,000 ppm.9. A laminated polyester film which comprises (1) the biaxially orientedpolyester film of claim 1 and a lubricating layer formed on at least oneside of the polyester film and which has (2) a haze value of 3% or lessand (3) a transmittance of ultraviolet radiation having a wavelength of365 nm of 86% or more.
 10. The laminated polyester film of claim 9,wherein the lubricating layer comprises (A) a copolyester having a glasstransition temperature of 40 to 80° C. and containing a dicarboxylicacid component having a group represented by —SO₃M (M is the sameequivalent as —SO₃ ⁻ of a metal atom, ammonium group, quaternary organicammonium group or quaternary organic phosphonium group) in an amount of8 to 20 mol % based on total of all the dicarboxylic acid components,(B) an acrylic resin having a glass transition temperature of 25 to 70°C., and (C) an inert particle lubricant.
 11. The laminated polyesterfilm of claim 10, wherein the average particle diameter of the inertparticle lubricant is smaller than twice the thickness of thelubricating layer.
 12. The laminated polyester film of any one of claims9 to 11, wherein the lubricating layer has a thickness of 5 to 200 nm.13. The laminated polyester film of claim 9 which contains metalantimony in an amount of 15 mmol % or less based on the total of all theacid components.
 14. The laminated polyester film of claim 9, whereinthe number of flyspecks having a long diameter of 20 μm or more is 0 to10 per 10 cm² of the film plane.
 15. The laminated polyester film ofclaim 9 which has a thermal shrinkage factor in a longitudinal directionafter 30 minutes of a heat treatment at 150° C. of 2% or less.
 16. Thelaminated polyester film of claim 9 which has a thermal shrinkage factorin a transverse direction after 30 minutes of a heat treatment at 150°C. of 2% or less.
 17. Use of the biaxially oriented polyester film ofclaim 1 as a base layer for the production of a dry film resist.
 18. Useof the laminated polyester film of claim 9 as a base layer for theproduction of a dry film resist.
 19. A dry film resist comprising thebiaxially oriented polyester film of claim 1, a photoresist layer and aprotective film layer formed in the mentioned order.
 20. A dry filmresist comprising the laminated polyester film of claim 9, a photoresistlayer and a protective film layer formed in the mentioned order, whereinwhen the laminated polyester film has a lubricating layer on only oneside, the photoresist layer is existent on a side devoid of thelubricating layer.